Move assembly newline function into common debug code

Printing a newline is a relatively common functionality for code to want
to do. Therefore, this patch now moves this function into a common part
of the code that anyone can use.

Change-Id: I2cad699fde00ef8d2aabf8bf35742ddd88d090ba
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>